LMB-1 is an immunotoxin composed of murine mAb B3 chemically coupled to a recombinant form of Pseudomonas exotoxin, NLysPE38 though a thioether bond. Phase I clinical trial to assess the toxicity, the pharmacokinetics, the immunogenicity and the anti-tumor activity of LMB-1 is being conducted at Medicine Branch, NCI. Patients with carcinomas of the colon, esophagus, stomach, pancreas, breast, lung, ovary or bladder, who have failed standard therapy are all potentially eligible. Paraffin blocks of the patients tumor tissue must express the B3 antigen on> 30% of the cells and the patient must not have neutralizing antibodies to LMB-l prior to therapy. Karnofsky performance> 80%, adequate liver, renal and bone marrow functions are required. The treatment is given by i.v. bolus over 30 minutes on days l, 3 and 5. All patients receive a 0.1 mg test dose on day l. This treatment can be repeated every 4 weeks, provided that the patient has not developed antibodies against LMB- 1. To date, 35 patients have been entered at doses ranging from 10 to 100 micrograms/kg/dose. Twenty six patients have colo-rectal cancer, 5 breast cancer, 1 gastric cancer, 1 esophageal cancer, l ca of the ampulla of Vater, 1 ovarian cancer. Seventeen patients were male and 18 were female. The median age was 45.5. The major side effect is Vascular Leak Syndrome (VLS), manifested by decrease serum albumin, weight gain and peripheral edema. Sinus tachycardia, hypotension and pulmonary edema was observed in one patient who received 100 micrograms/kg. Other less common side effects included flu like symptoms, headache, low grade fever, low voltage and nonspecific T wave inversion. The MTD has not been reached but probably is close to 100 crograms/kg.